Alexandrian laurel (Danae racemosa L.) is a highly desirable species but is difficult to germinate and propagate. It is one of the finest of broadleaf, dark evergreen shrubs with branches arching to three feet in height and four feet wide. The shrub is an excellent choice for both woodland and shade gardens and is highly demanded by landscape architects and designers. In addition, there is some interest in the antinociceptive (i.e. increasing tolerance for pain) properties of extracts and flavonoids isolated from leaves of Alexandrian laurel. Currently, United States is importing almost all Alexandrian laurel cut foliage for flower arrangement from Italy and other countries.
Once established in proper growth conditions, Alexandrian laurel requires little intervention, such as disease and insect control, watering, and wild animal resistance. Normal propagation for this species is by seeds and division. Conventional seed germination takes up to a year and half with a success rate of only about 20%. It typically takes up to six years to produce a one-gallon size plant, such as the size generally sold by greenhouses. The long period of germination and slow growth adversely affect its commercial availability.
Agricultural biotechnology is important for the farming community in agriculture, horticulture and forestry. Ag-biotech approaches include in vitro culture techniques, including tissue culture and micropropagation. The in vitro techniques are especially notable in horticulture because of the demonstrated potential for mass production of targeted plant materials. In vitro culture techniques generally involve placing a small piece of plant material in a container such as a test tube, a Petri dish, or a baby food jar containing culture medium with balanced nutrients. Due to the space savings associated with in vitro culture methods, they can reduce energy costs associated with growing young plants. This technique can be useful for mass production of plants with unique characteristics and plants that are difficult to propagate, including those with low germination rates. However, this technique is generally species-specific and detailed steps and formulae for each plant species require intensive scientific research.
Micropropagation can be cost-effective and useful for farmers and nursery owners with limited resources, as once they learn basic aseptic techniques, these growers can use micropropagation techniques to follow scientifically proven processes to produce a highly desirable plant. This technique can also produce disease-free plants that can be used as disease-free seedstock, which is particularly useful for horticultural crops. However, plant species with unique quality and/or characteristics are often difficult to propagate; this is true for woody plant species, such as Alexandrian laurel.
A number of issues remain in the propagation of Alexandrian laurel, including: (a) a limited numbers of seeds available for commercial sale, due to the slow growth of the plant; (b) very low multiplication rate, as only one seedling grows from each seed; and (c) unbalanced seedling growth observed where the seedlings have with too much root growth and too little shoot growth.
Thus, an efficient propagation protocol to produce high quality Alexandrian laurel plants in a shorter germination period is needed. Also needed is a process that allows for efficient germination, enhancement of seedling quality, and the production of multiple seedlings per a single seed.